1. Technical Field
Generally, the invention relates to a vertical support. Particularly, the invention relates to a tripod having support legs which automatically open and close when the tripod is placed on a support surface and lifted from the support surface, respectively, and having a self-contained battery. Specifically, the invention relates to a tripod having a telescopic center post on which the support legs are pivotally mounted and in which the battery is contained, and a plurality of coupling links pivotally attached at one end to a bottom end of the center post and pivotally attached at the other end to the support legs whereby the pivotal attachment to the support legs is offset toward an outer edge thereof causing the automatic opening of the tripod.
2. Background Information
Tripods are commonly used in the video and photographic industries to support and stabilize equipment such as cameras, lights, and background screens. Typically, tripods include at least three pivotally mounted support legs movable between open and closed positions. In the open position, the support legs extend angularly downward with the three legs being separated by approximately 120 degrees. The support legs stabilize the tripod in a vertical position and prevent movement of the video equipment during use thereof. The tripods often have telescopic legs or a telescopic center post to allow a user to adjust the height of the equipment being mounted on the tripod. The legs of the tripod pivot to the closed position whereby all three legs extend generally adjacent and parallel to one another.
One problem with this type of prior art tripod is the time intensive and awkward process of pivoting the support legs to the open position. Each support leg must be independently moved to the open position and telescopically adjusted to the proper height, often while the user is carrying expensive and fragile video or photographic equipment. When the user has adjusted one of the three legs to the desired position, the tripod must be balanced on that leg while the user simultaneously adjusts the remaining legs creating an unbalanced and unstable situation. Similar problems are encountered when moving the legs from the open position to the closed position.
Several prior art tripods have been developed which disclose a mechanism to easily open the support legs of a tripod or similar structure. For example, U.S. Pat. No. 609,295 discloses a tripod for supporting a bicycle having three support legs pivotally mounted to a center post and movable between an open and closed position. The support legs are pivotally connected to an upper sleeve which slides along the center post to open and close the tripod. A set screw is attached to the sleeve to retain the legs in an adjusted position.
U.S. Pat. No. 1,456,356 discloses a rack having a center post with four support legs pivotally mounted to a runner. As the runner slides down the post, the legs pivot to a divergent position. A plurality of braces attach each support leg to an adjacent support leg and to the center post.
U.S. Pat. No. 2,709,560 discloses a tripod having upper and lower telescopically engaged cylinders with a compression spring extending within the cylinders. Three support legs are pivotally mounted to a collar which slides vertically along the outer surface of the lower cylinder to move the support legs between open and closed positions. Each support leg includes a telescopic section which allows the length of each leg to be independently adjusted. The coil spring supports a camera and the like in a relatively floating position to allow the camera to be easily raised or lowered with only a small amount of effort to be applied in the direction of desired movement.
U.S. Pat. No. 3,696,856 discloses a swivel standard for portable projection screens having tripod legs pivotally mounted on a top bracket. The bracket is loosely slidable along a center post and opens and closes the support legs as the bracket slides downward and upward, respectively, along the center post.
U.S. Pat. No. 3,841,594 discloses a collapsible projection screen which is supported by a tripod base having three collapsible support legs pivotally mounted to an upper collar. The collar slides vertically along a center post to open and close the support legs. A bracing link is pivotally attached to each leg and to a stationary bottom collar.
U.S. Pat. No. 4,705,251 discloses a self-erecting tripod apparatus having three outwardly extending legs which are attached to a lower rod which telescopically engages an upper sleeve intermediate the three legs. When the center rod is lowered onto a support surface, the support legs are automatically extended to an outward open position and when the apparatus is lifted from the support surface the support legs will collapse to a closed position under the influence of gravity. A vertically slidable collar extends around the center rod and includes a plurality of links pivotally mounted to the collar and to the support legs. The support legs move between the open and closed positions as the bottom collar moves upwardly and downwardly, respectively, along the center rod.
U.S. Pat. No. 4,826,187 discloses a collapsible monopod cart having a frame with a pair of wheels and camera mounting monopod which is offset forwardly from the axis of the wheels. The monopod has a selectively extensible and retractable ground engaging leg assembly which, when extended, forms a polygonal stabilizing base in conjunction with the wheels. The cart further includes equipment supporting surfaces and enclosure members which allow a user to carry and protect equipment on the cart even when in the collapsed position.
Although these tripods and supporting devices are adequate for the purpose for which they are intended, all but one of these prior art tripods require some degree of manual adjustment to move their support legs between the open and closed positions. Only U.S. Pat. No. 4,705,251 discloses a tripod which automatically opens when the tripod is placed on a support surface and automatically closes when the tripod is lifted from the support surface. One problem with the '251 patent is that the legs must be angled slightly outwardly even when the tripod is in the closed position biasing the legs toward the open position to facilitate the automatic opening thereof If the legs of the '251 tripod were to extend vertically adjacent the center post when in the closed position, the downward pressure applied when the tripod is placed on a support surface will not be directed outwardly to automatically open the support legs.
The tripod of the present invention improves upon the '251 patent by offsetting the pivotal attachment of the coupling links to the support legs to bias the legs outwardly while allowing the support legs to pivot to a vertical position parallel and adjacent to the center post when in the closed position. By allowing the support legs to close to a vertical position, the tripod of the present invention requires less space than the '251 tripod to store and transport.
Another problem that photographers and videographers encounter when using various video equipment on a tripod is that the video equipment such as video cameras and lights require an external battery to operate for extended periods of time. Conventionally, the user of the video equipment would carry the battery around his or her shoulder with an electrical cord extending from the battery to the video equipment mounted on the tripod. Often the user will forget that the user is connected to the tripod by the electrical cord and will step away from the tripod pulling the tripod over and possibly damaging the expensive video equipment mounted thereon. Another method used to connect the battery to the video equipment is to strap the battery directly to the tripod using, for example, duct tape. This method puts the tripod in an unbalanced configuration allowing the tripod to be easily knocked over when bumped.
Therefore, the need exists for a tripod having support legs which automatically open and close when the tripod is placed on a support surface and when removed from the support surface, respectively, which allows the support legs to close to a vertical position parallel and adjacent to the center post when in the closed position, and which has a self-contained battery which maintains the balanced configuration of the tripod.